drm/i915: Force VDD off on the new power seqeuencer before starting to use it

Apparently some VLV BIOSen like to leave the VDD force bit enabled
even for power seqeuncers that aren't properly hooked up to any
port. That will result in a imbalance in the AUX power domain
refcount when we stat to use said power sequencer as edp_panel_vdd_on()
will not grab the power domain reference if it sees that the VDD is
already on.

To fix this let's make sure we turn off the VDD force bit when we
initialize the power sequencer registers. That is, unless it's
being done from the init path since there we are actually
initializing the registers for the current power sequencer and
we don't want to turn VDD off needlessly as that would require
waiting for the power cycle delay before we turn it back on.

This fixes the following kind of warnings:
WARNING: CPU: 0 PID: 123 at ../drivers/gpu/drm/i915/intel_runtime_pm.c:1455 intel_display_power_put+0x13a/0x170 [i915]()
WARN_ON(!power_domains->domain_use_count[domain])
...

v2: Fix typos in comment (David)

Cc: [e-mail]
Cc: Matwey V. Kornilov <[e-mail]>
Tested-by: Matwey V. Kornilov <[e-mail]>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98695
Signed-off-by: Ville Syrjälä <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]
Reviewed-by: David Weinehall <[e-mail]>
(cherry picked from commit 5d5ab2d26f32bdaa5872b938658e0bf8d341bc4c)
Signed-off-by: Jani Nikula <[e-mail]>

drivers/gpu/drm/i915/intel_dp.c

···
 				    struct intel_dp *intel_dp);
 static void
 intel_dp_init_panel_power_sequencer_registers(struct drm_device *dev,
-					      struct intel_dp *intel_dp);
+					      struct intel_dp *intel_dp,
+					      bool force_disable_vdd);
 static void
 intel_dp_pps_init(struct drm_device *dev, struct intel_dp *intel_dp);
 
···
 
 	/* init power sequencer on this pipe and port */
 	intel_dp_init_panel_power_sequencer(dev, intel_dp);
-	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp);
+	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp, true);
 
 	/*
 	 * Even vdd force doesn't work until we've made
···
 	 * Only the HW needs to be reprogrammed, the SW state is fixed and
 	 * has been setup during connector init.
 	 */
-	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp);
+	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp, false);
 
 	return 0;
 }
···
 		      port_name(port), pipe_name(intel_dp->pps_pipe));
 
 	intel_dp_init_panel_power_sequencer(dev, intel_dp);
-	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp);
+	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp, false);
 }
 
 void intel_power_sequencer_reset(struct drm_i915_private *dev_priv)
···
 
 	/* init power sequencer on this pipe and port */
 	intel_dp_init_panel_power_sequencer(dev, intel_dp);
-	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp);
+	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp, true);
 }
 
 static void vlv_pre_enable_dp(struct intel_encoder *encoder,
···
 
 static void
 intel_dp_init_panel_power_sequencer_registers(struct drm_device *dev,
-					      struct intel_dp *intel_dp)
+					      struct intel_dp *intel_dp,
+					      bool force_disable_vdd)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
 	u32 pp_on, pp_off, pp_div, port_sel = 0;
···
 	lockdep_assert_held(&dev_priv->pps_mutex);
 
 	intel_pps_get_registers(dev_priv, intel_dp, &regs);
+
+	/*
+	 * On some VLV machines the BIOS can leave the VDD
+	 * enabled even on power seqeuencers which aren't
+	 * hooked up to any port. This would mess up the
+	 * power domain tracking the first time we pick
+	 * one of these power sequencers for use since
+	 * edp_panel_vdd_on() would notice that the VDD was
+	 * already on and therefore wouldn't grab the power
+	 * domain reference. Disable VDD first to avoid this.
+	 * This also avoids spuriously turning the VDD on as
+	 * soon as the new power seqeuencer gets initialized.
+	 */
+	if (force_disable_vdd) {
+		u32 pp = ironlake_get_pp_control(intel_dp);
+
+		WARN(pp & PANEL_POWER_ON, "Panel power already on\n");
+
+		if (pp & EDP_FORCE_VDD)
+			DRM_DEBUG_KMS("VDD already on, disabling first\n");
+
+		pp &= ~EDP_FORCE_VDD;
+
+		I915_WRITE(regs.pp_ctrl, pp);
+	}
 
 	pp_on = (seq->t1_t3 << PANEL_POWER_UP_DELAY_SHIFT) |
 		(seq->t8 << PANEL_LIGHT_ON_DELAY_SHIFT);
···
 		vlv_initial_power_sequencer_setup(intel_dp);
 	} else {
 		intel_dp_init_panel_power_sequencer(dev, intel_dp);
-		intel_dp_init_panel_power_sequencer_registers(dev, intel_dp);
+		intel_dp_init_panel_power_sequencer_registers(dev, intel_dp, false);
 	}
 }